There are basically two techniques for accessing media content over a data network, e.g. the Internet; streaming, which means that the user receives a continuous stream of media (equivalent to listening to radio), and clip-by-clip downloading which means that the user selects and downloads the media content clips one by one (equivalent to buying each song on a CD separately). None of these techniques by itself offers the user any satisfying personalized media experience.
Different technologies have therefore been developed to accomplish a more personalized media access, with the common object of delivering an optimized media experience to the user, normally including a selection of the media content that is deemed most interesting for the user. This object has been particularly highlighted as the access of mobile Internet has increased.
According to a first approach, the user utilizes a handheld device that normally is not connected to the network. Instead, the device is connected sporadically to the network, typically using docking equipment of some kind. An example of this approach is the AvantGo system, applicable for example with a Palm Pilot device. The user initiates an account at the AvantGo server, and selects a number of servers from which he/she would like information from. This information, which has a special memory-economic format, is then downloaded to the AvantGo server and continually updated. Each time the user docks the Palm Pilot, the current information is downloaded to the Palm Pilot. Then, with the Palm Pilot disconnected from the network, the user can browse among the downloaded pages, for example during a bus ride home. Obviously, this approach has severe limitations in terms of dynamics and media quality. Firstly, as the device is not connected during browsing, the information contents can not be changed. Secondly, the media information is limited to text and simple graphics, in order to be compatible with the docking procedure and to be sufficiently compact to allow a great number of pages to be stored in the Palm Pilot. Also, the docking routine is typically performed while the user waits, for example before leaving his/her workplace for the day. Therefore, it is desirable that the docking routine is performed as quickly as possible, making it too time-consuming to transfer media contents of any greater volume, as sound, video etc., even though the connection itself is of high quality.
According to a second approach, the user uses a handheld device to actively access all available information on the network. The device, for example a WAP-telephone or a GPRS-device, can be connected continuously and works as a handheld network browser. This approach puts practically no restraints on the amount of information available to the user, except restrictions in the form of network capacity and display/navigation limitations of the handheld device. At the same time, however, the user is requested to actively take part in the information seeking, by browsing the Web. As the modern information seeker typically is in a hurry, there is a need for a more personalized media access. Also, when browsing in search of a subject, it is a known phenomenon that the Internet can lead a user away in the wrong direction. When sitting at home, this is normally not a problem, but a user on the run is not ready to wait for the media experience. A contributing factor to the impatience is the fact that a mobile Internet connection normally is charged in relation to how much information the user downloads, making it economically preferable to download selectively.
A third approach relates to “channels”, e.g. Active Channels in Windows 98 , originally developed for the Internet user who is not constantly connected, in order to maximize the use of the connection. A channel is a kind of subscription of a media content, such as a magazine or a news station. By initializing a channel, the user requests this media content to be downloaded to the client while the user is on-line, with a minimum of disturbance of the user's other on-going Internet communication. Then, when the user goes off-line, the media content is available from a client memory device (e.g. the hard disc). The channel concept can be implemented on handheld devices, and then offers a selected media content to the user. The channel content can be further personalized by e.g. cookies, thereby making the media experience even more optimized. A problem with the channel approach is that although the user is given a more efficient media experience, there is still a risk of downloading excessive information. No matter how personalized a channel is designed, if a user decides not to study its contents, these contents were downloaded for no purpose, causing an unnecessary cost.
Another problem, present in all media information delivery over a permanent mobile link, is the risk of deterioration of the connection quality. This can occur when a car enters a tunnel, or when a moving person is located in between the zones of different cells in a cellular network (e.g. GPRS). If the line quality decreases, normal browsing can be tediously slow, making a satisfying media experience difficult.
Additionally, in order to play back the media content the user's hardware device (e.g. a PC or a handheld device) must include a media player supporting the specific media format. The media player is a computer program running on the hardware device, e.g. an MP3 player. If the media player does not support the media. format, the user will not be able to benefit from the download, causing unnecessary cost in terms of connection capacity.
The media content is typically stored as a sequence of data bits, a file, formatted according to a pre-defined standardized data format, e.g. WAV or MP3. The file typically contains one and only one media content clip, e.g. a song, together with some very limited information about the media content itself, e.g. title, artist and genre.
The media content is typically played clip-by-clip, i.e. one file is selected and opened in the media player (the clip is played) and when the end of the file is reached the audio clip (e.g. the song) is finished. In order to play the next clip, the clip has to be selected and started explicitly. Some media players support a playlist concept where the clips can be played in a certain pre-defined order but these playlists are extremely limited, as they can only express a linear (one dimensional) sequence of clips. Furthermore, there exists no standard data format to define a playlist.
Some of the above problems have been addressed by MPEG (Moving Picture Expert Group), and are mentioned in the report MPEG-21 Multimedia Framework, Beijing, 2000.